Process Integration And Optimization Of Phase Change Memory

The phase-change random access memory (PCRAM) storage mechanism is based on the fast resistance converting and reversible phase-change transition of chalcogenide alloy (e.g., Ge2Sb2Te5, GST). As a novel non-volatile memory, there are great differences in electrical operating mechanism and process integration method between PCM and other kinds of traditional non-volatile memory. Therefore, it is significant that PCM cell structure design, PCM process integration scheme and phase change materials selection should be done before mass production. In this work, the optimized PCM process scheme has been proposed, which is based on device simulation and process experiment result. Mainly include:1. The process integration scheme has been proposed for PCM. The PCM cells with ring type electrode and side wall electrode have been studied. Compared with the PCM cell with traditional electrode, the cells with ring type electrode and side wall electrode can reduce power consumption, improve PCM array density and be benefit for process integration. And the process schemes of ring type electrode and side wall electrode cell have been optimized, which can be used for mass production in different technology nodes.2. The treatment and deposition solution for the phase change material have been investigated for PCM application. The deposition process of phase change film is a ee*e critical process for PCM manufacture. In different deposition temperatures, phase change materials with diversity of chemical constituents perform different film qualities and characteristics. And the adhesion between phase change material and dielectric material are poor under high temperature. In this work, an improved phase change material deposition process with pre-process method has been proposed for product process by means of phase change film delaminating and peeling defect analysis.3. The electrode loop process scheme is another key step of the entire process flow. The vertical side wall electrode and traditional electrode PCM cells has been studied. It demonstrates that the PCRAM cell with improved side wall electrode process scheme can be fully compatible with silicon mass production.4. The failure bits in PCM array can be identified by electrical testing and failure analysis, and improved PCM process integration scheme has been proposed for bit yield rate.